The objectives of this study are to assess the role of ticks as the source of canine Borrelia burgdorferi infections and to develop more effectual diagnostic tests for canine LD. In addition, the role of immunosuppression in canine LD will also be investigated. A two-year study of dogs from an area where human LD has occurred is proposed. Ticks and other hematophagous arthropods will be recovered from the dogs and tested by IFA for the presence of B. burgdorferi. Blood will be collected from the dogs and tested for sero-conversion to the pathogen. In a related laboratory study, normal and immunosuppressed dogs will be inoculated with B. burgdorferi and the status of each dog monitored using a clinical evaluation score. It is expected that the resulting data will have significant implications for methods of diagnosis and the incidence of LD that will be useful in risk assessment for humans. The specific aims are: 1) To determine which tick species are involved in transmission of canine LD in Alabama. 2) To evaluate the use of ear-punch biopsies and the examination of urine samples for the diagnosis of canine Lyme disease. 3) To determine the role of immunosuppression prior to exposure in clinical canine LD.